Before and during the Civil War additions were made to the original wings. While the exterior of the building was constructed along the lines of the original Mills wings, the interiors of the later wings reflect changes in both building technology and aesthetic taste. Iron columns and beams reinforced the building's brick vaults, and the architectural detailing became much more ornate. The final addition to the Treasury Building was the north wing, built from 1867 to 1869. Its architect was Alfred B. Mullett, who later designed the Old Executive Office Building on the west side of the White House. The north wing is the site of the Cash Room - a two-story marble hall where the daily financial business of the U.S. Government was transacted. In 1869, the Cash Room was used for President Grant's inaugural reception.